The invention relates to an injection device of the single-use type, which is designed to be pre-filled with a dose of liquid, in particular a medicinal liquid, to be injected.
Single-use injection devices which are designed to be pre-filled comprise a syringe body, which is either provided with a base, in which there is sealed a needle, which is protected by a protective cap, or comprise a conical male locking connection, which makes it possible to fit onto the said syringe body a conical female locking connection, which supports an injection needle protected by a protective cap, the said conical connections defining an assembly which is commonly known as a xe2x80x9cLxc3x9cER conical assemblyxe2x80x9d.
The most conventional injection devices, known as the xe2x80x9cwet needlexe2x80x9d type, are of the type provided with a syringe body comprising a base, in which there is sealed an injection needle, which is closed off by means of a protective elastomer cap, which is provided with a inner blind bore contained in the base of the said cap, inside which the end of the said needle is forced, such as to guarantee the sealing of the injection device before injection takes place.
The first disadvantage of injection devices of this type consists in the fact that when the protective cap is put into place, the injection needle must be centred perfectly in relation to the bore in the said cap. However, in practice, this centring is sometimes approximate, such that fitting of the cap frequently leads to deterioration of the said cap or needle, resulting in significant numbers of production rejects.
In addition, according to this principle, the quality of the needle (sharpness, silicone coating), is systematically affected by the occurrence of friction of the point of the said needle against the inner wall of the blind bore in the cap, when the latter is forced on.
Finally, the liquid contained in these injection devices is necessarily in contact with the materials which constitute the injection needle and the protective cap, which, for certain types of liquid, can affect the conservation of the latter.
In order to eliminate these disadvantages, numerous injection devices known as the xe2x80x9cdry needlexe2x80x9d type have been designed, wherein the injection needle is isolated from the liquid contained in the syringe body until the moment of injection.
A first type of xe2x80x9cdry needlexe2x80x9d injection device is that which is commonly used in dentistry, and comprises a bottle, which contains the liquid to be injected, and is closed off by a membrane, and a double-point needle, which can be displaced axially relative to the said bottle, such as to pierce the membrane at the moment of injection. Injection devices of this type are described in particular in patents DE-847473, FR-2347055, U.S. Pat. No. 4,639,250, EP-602883, DE-2008751, DE-1909794.
This type of injection device has two sorts of disadvantages. In fact, firstly, the fact of needing a double-point needle leads to a increase in the cost price of these injection devices, derived firstly from the cost of the said needle itself, and secondly from the necessity of carrying out two sharpening operations instead of a single sharpening operation required for a conventional needle. In addition, for needles with a small diameter, it often happens that problems of coring arise, leading to the inclusion of particles of membrane inside the aperture of the needle, which either close off this aperture, or are injected together with the liquid.
A second type of xe2x80x9cdry needlexe2x80x9d injection device comprises a syringe body which accommodates two stoppers, which delimit the chamber containing the liquid, and onto which there is crimped a base, which either supports a needle, or is of the male conical connection type, the said syringe body additionally having a compartment which is provided with a duct for communication with the injection needle, which is disposed such as to be put into contact with the chamber only after the pistons have been displaced axially.
Injection devices of this type, which are described in particular in patents FR-2412320, FR-2208684, EP-191508, EP-588148 and EP-720857, make it possible to eliminate the disadvantages of the above-described injection devices. However, they themselves also have two disadvantages. In fact, firstly, the operation of crimping the base onto the syringe body is problematic, and requires particular care in order to guarantee perfect sealing between the said base and the said syringe body. In addition, and above all, injection devices of this type can be subject to accidental escape of the liquid contained in the chamber, resulting for example from expansion of the volume of gas contained in the said chamber, or from depressurisation, in particular during transport by air, which lead to axial displacement of the stopper for access to the compartment for discharge of the liquid.
A third type of xe2x80x9cdry needlexe2x80x9d injection device, described in particular in patents EP-150681, EP-111796, FR-2330413 and WO-8404252, makes it possible to eliminate all of the above-described disadvantages. For this purpose, these injection devices comprise firstly a syringe body, which is provided with a chamber closed off by a rubber stopper, which contains a longitudinal through-bore, and secondly, a base which either supports a needle, or is of the male conical connection type, is mobile axially inside the bore of the said stopper, and is provided with ducts which are disposed such as to put the injection needle and the chamber into communication during axial displacement of the said base, which tends to thrust the latter into the stopper.
The present invention relates to an injection device of the locking conical assembly type, with a design similar to that of the injection devices of the third type described above, and the main objective of which is to provide an ergonomic injection device, which combines the advantages of these injection devices (sealing, guarantee against risks of accidental escape, etc), the activation of which for the purpose of an injection is carried out very simply, by means of a very natural gesture.
For this purpose, the invention relates to an injection device comprising a syringe body, which delimits a chamber which is designed to be filled with a liquid, in particular a medicinal liquid, and a unit for closing off the chamber and distributing the liquid, comprising an end piece for closing off the said chamber, which is extended by a locking male conical connection, provided with a duct for distribution of the liquid, the said unit for closing off and distributing being mobile axially between a position known as the closing-off position, in which the distribution duct is isolated from the chamber of the syringe body, and a position known as the injection position, in which the said distribution duct communicates with the said chamber.
According to the invention, this injection device is characterised in that:
the unit for closing off and distributing comprises an intermediate section, which is disposed between the closing-off end piece and the male conical connection, and is placed such as to extend in the extension of the syringe body;
the syringe body comprises a ring which is provided with a front wall, in which there is provided an axial opening for passage of the conical male connection, the said ring:
delimiting two inner, upper and lower compartments which are juxtaposed axially, each of which has a shape which is conjugated with the intermediate section of the unit for closing off and distributing, and can accommodate the said intermediate section, the said compartments being separated by axial stop units which can permit axial displacement of the intermediate section of one compartment towards the other compartment; and
comprising in the extension of the front wall a sleeve which is threaded internally, and is designed to accommodate the male conical connection and to act as a fixed nut for assembly of a locking female conical connection which supports an injection needle.
Activation of an injection device of this type, for the purpose of the injection, is thus obtained automatically during assembly by screwing of a female conical connection onto the syringe body, which gives rise to axial displacement of the unit for closing off and distributing, of the upper compartment of the ring, towards the lower compartment of the said ring, resulting in the needle and the chamber of the syringe body being put into communication.
This activation is thus derived from simple fitting onto the injection device of a female conical connection which constitutes a conventional conical assembly, for example of the xe2x80x9cLxc3x9cERxe2x80x9d type.
In addition, the axial displacement of the unit for closing off and distributing is irreversible, owing to the fact that any further, inverse displacement, is subsequently prevented.
According to another characteristic of the invention, the ring has in its interior an annular neck which forms the top of two longitudinal divergent sections, and constitutes the axial stop means for separation of the upper and lower compartments, the intermediate section of the unit for closing off and distributing having a shape and dimensions which are conjugated with the upper compartment of the said ring.
Additionally, the injection device according to the invention advantageously comprises a closing-off stopper with dimensions which are suitable for being inserted in the syringe body, provided with a through bore which opens into the said syringe body at a countersink.
In addition, in this case, the unit for closing off and distributing has dimensions which are designed to be inserted in the bore in the closing-off stopper, and comprises a distribution duct containing a transverse branch, which is disposed such as to be positioned recessed from the countersink in the said closing-off stopper, in the closing-off position of the unit for closing off and distributing, and to extend into the said countersink, in the injection position of the said unit.